Gasoline composition



Nov. 20, 1962 R. E. SUTTON ET AL 3,065,065

GASOLINE COMPOSITION Filed March 29, 1960 6.0 cc TEL/GAL.

4.0ccTEL/GAL.

INCREASE IN 0. N. FROM ADDITION OF CO-ANTIKNOCK AGENT 0 l l O l 2 3 4 5METAL CONCENTRATION, MILLIMOLES/GAL.

INVENTORS:

REID E. SUTTON JOHN L. BAME THEIR ATTORNEY United States Patent3,065,065 GASOLINE COMPOSITION Reid E. Sutton and John L. Bame, EastAlton, 11]., as-

signors to Shell 0i! Company, New York, N.Y a cor poration of DelawareFiled Mar. 29, 1%0, Ser. No. 18,301 15 Claims. (Cl. 44-69) Thisinvention relates to improved hydrocarbon fuel compositions andparticularly to improved motor gasoline fuel compositions having highoctane numbers.

Recent automotive design trends have been toward engines having greaterpower for the same size engine and more efficient utilization of thegasoline fuel. Engine designers have accomplished this largely bysteadily raising the compression ratios of automotive engines, which hasnecessitated the use of fuels having increased resistance to detonationor spark knock. There is also an increased demand for aviation fuelshaving greater anti-knock properties. It has heretofore been possible tomanufacture such fuels from crude petroleum by the development andutilization of new hydrocarbon conversion and synthesis processes suchas cracking, reforming, polymerization, and alkylation. The resistanceto knock of the fuels from these processes is even further augmented bythe addition of antiknock agents such as tetraethyllead (TEL), and,recently, methylcyclopentadienyl manganese tricarbonyl. Resistance tospark knock is, of course, evaluated as octane number. Therefore, thedemand for fuels having greater resistance to spark knock is manifestedin the constantly increasing octane number of premium fuels. However, asthe octane number of modern gasoline fuels has been raised, there hasbeen a concomitant decrease in the susceptibility of such fuels tooctane number improvement by addition of organo-metallic antiknockagents. It becomes less economical, therefore, to obtain greaterresistance to spark knock by this means with higher octane number fuels.In addition, the amount of organo-metallic additive which is added tomotor fuels may also be limited by consideration of the degree oftoxicity imparted to the 'fuel containing such materials. For thisreason, the maximum amount of tetraethyllead which may be added tocommercial gasoline motor fuels is 3 or 4 cc./ gal. (US) and 6 cc./gal.(US) for automotive and aviation fuels, respectively. Consequently, thedegree of octane number improvement which can be obtained in this manneris limited. Organo-metallic antiknock additives are difficult tosynthesize and are expensive. Their addition to fuels is thus limited tosmall concentrations by considerations of economics as well. Yet anotherlimitation on the use of such antiknock additive-containing fuels is thetendency of the antiknock additives therein to lay down large quantitiesof deposits in the combustion chamber of the engine, which maycontribute to an increase in the octane number requirement of theengine. Because of these limiting factors on the use of conventionalorgano-metallic antiknock additives, the octane number obtainable fromgasoline fuels made by conventional refining processes has also beenlimited.

There have been many attempts to solve this problem by the use of two ormore antiknock agents. However, in most of these situations, theincremental increase in octane number obtained by adding the secondantiknock agent has been considerably less than the octane numberincrease obtainable when the supplemental antiknock agent is added tothe gasoline by itself. That is, the antiknock activity of thesupplemental antiknock agent or of both antiknock agents is less, on thebasis of the volume added, than either by itself. Consequently, eventhough significant increases in octane number are ob- Patented Nov. 20,1962 tainable, it has heretofore been uneconomical to obtain higheroctane number motor gasoline in this manner.

It is therefore an object of this invention to provide improved gasolinefuel compositions. It is also an object of the invention to augment theefiicacy of tetraethyllead as an antiknock additive in gasoline. It is afurther object of the invention to provide higher detonation resistancein gasoline in an economical manner. It is still another object toprovide hydrocarbon compositions which enhance the efficiency ofantiknock additives added thereto. Another object is to attain theforegoing objects without detrimental side effects in the use of thefuel in gasoline engines. A still further object of the invention is toprovide an improved antiknock additive concentrate composition.

The attainment of these and other objects will be apparent from thedetailed description of the invention which is a gasoline motor fuelcomposition containing a tetraalkyllead compound as a primary antiknockagent and small but critical amounts of certain organo-metalliccompounds which by themselves exhibit no primary antiknock activity, andfrom the drawing, consisting of a single figure, which illustratesgraphically the effect of the antiknock agent upon the octane number ofgasoline containing various quantities of tetraethyllead.

The use of orgauo-metallic compounds as primary antiknock agents haslong been known, and countless numbers of these materials have beensuggested, tried, and used with various degrees of success. The mostwidely used for many reasons, including availability, economy, andantiknock activity, are the tetraalkylleads, particularlytetraethyllead. However, it has now been found that certainorgano-metallic compounds, which possess essentially no primaryantiknock activity when they are added to gasoline containing no otherantiknock agent, nevertheless when added to leaded gasolines of selectedcomposition as to hydrocarbon type and boiling range, possessextraordinary co-antiknock activity. By co-antiknock activity, it ishere meant that the secondary or co-antiknock agent causes the octanenumber of the gasoline containing both primary and secondary antiknockadditives to be raised significantly above the level which is obtainedby the primary antiknock agent alone, the co-antiknock effect being theresult of co-action of the secondary with the primary additive ratherthan any primary antiknock properties of the secondary additive alone.

The addition of very small amounts of organo-metallic compoundscorresponding to the structural formula to fuels containingtetraalkyllead primary antiknock agents has been found to raise theoctane number of the total mixture by as much as 4.5 octane numbers oreven more.

In the foregoing structural formula Y (ZAY)mM M is a metal selected fromthe group consisting of antimony, bismuth, cobalt, copper, nickel andtellurium, A is selected from the group consisting of carbon andphosphorus, and Z is selected from the group consisting of (RY) when Ais phosphorus and (R X) when A is carbon. The symbol Y denotes achalcogen atom having an atomic number of from 8 to 16, inclusively, Xis selected from the group consisting of nitrogen and chalcogen havingan atomic number of from 8 to 16, inclusively, and R is a monovalenthydrocarbyl group containing from 3 to 15 carbon atoms per molecule. Thesymbol n denotes a whole number of from. 1 to 2 which is one less thanthe valence of X, and m is a whole number corresponding to the valenceof M.

The enhancement of octane number quality afforded by the addition ofextremely small quantities of organic metallic compounds correspondingto the foregoing formula may be observed by reference to the followingexample.

EXAMPLE I A number of compounds corresponding to the formula Y 7 (ZAY)mMwere each added in the same concentration to separate samples of acommercial light olefin isobutane alkylate containing 3 cc.tetraethyllead (TEL) per US gallon. The octane number of all the samplescontaining secondary additive and also a separate sample of the samealkylate containing only 3 cc. TEL/gal. (US) Were determined by theResearch Method. (ASTM test designation D3S753). To determine theincrease in octane number obtained by adding small amounts ofco-antiknock agent, the difference in the octane numbers of the sampleswith and without co-antiknock agent (A O.N. were calculated. The resultsare tabulated below.

TABLE I Octane number, enhancement Concentration, millimoles/ gallonSecondary antiknock agent, composition Only metals from periodic groupsI, V, VI and VIII have been found to be effective. The members of groupsI and VIII having atomic numbers of from 27 to 29, inclusively, havebeen found to be particularly effective and are therefore the preferredmetallic constituents (M) of the co-antiknock agent in accordance withthe invention. Copper is particularly preferred.

Composition of the hydrocarbyl group R in the foregoing formula for theco-antiknock agents of the invention is important even though a Widerange of compositions may be used. It has been found that R must containat least 3 carbon atoms per molecule, but may contain as many as 15carbon atoms per molecule. The configuration of R is, however, notnarrowly critical. Thus, R may be alkyl, aryl, arylalkyl, alkylaryl,alkenyl, or cycloalkenyl.

The R group may also be substituted with, for example, halogen atoms andoxygen-containing groups such as hydroxyl, epoxy, and keto oxygen atoms.However, such substitutions must be limited to the extent that thehydrocarbon solubility of the compound is not substantially reduced. Itis preferred that the co-antiknock agents be completely soluble ingasoline hydrocarbons. In any event, the solubility of the co-antiknockagent must not be less than about 80% by volume, below which thecoantiknock action of the compounds is likely to be considerably reducedbecause of maldistribution to the cylinders of the engine.

When A is carbon, X is nitrogen, and Y is sulfur, i.e., when thecompound is a dithiocarbamate, it is particularly preferred that the twoRs are both alkyl groups with from 4 to 8 carbon atoms.

The data in the foregoing table, of course, show that large increases inoctane number are obtainable at extremely low metal concentrations. Inview of the fact that the increases obtained were of the same magnitudeas that obtained with many primary antiknock materials at much higherconcentrations, for example, 15 to 30 millimoles per gallon, it isapparent that the organo-metallic secondary anti-detonant materials arenot acting in the manner of a primary antiknock agent. That is, thesecondary antiknock additives are acting in conjunction with orco-acting with the tetraethyllead. As confirmation of this, thefollowing tests were performed.

EXAMPLE II Several metal dialkyldithiocarbamates were each added inamounts varying from 1 to 10 millimoles of copper per gallon (US) offuel to each of several samples of a commercial alkylate containing 3cc. TEL/ gallon (US). The Research Octane number of each samplecontaining the metallic co-antiknock agent and also a sample containingonly TEL and no co-antiknock compound were then obtained. By subtractingthe octane number of the blend containing no co-antiknock agent from theoctane number of the blends containing co-antiknock agent, a meassure ofthe octane number enhancement (A O.N.) at various ratios ofmetal-to-lead was obtained. The results were as follows:

TABLE II Copper Diamyldithloearbamate Concentration of metaldialkyldithiocarbamate A O.N. Millimoles Millimoles Grn. metal/ metal/metal/gal. gm. Pb millimole Pb (US) Copper Dioctyldithiocarbamate NickelDioctyldithiocarbamate Cobalt Dioctyldithiocarbamate The above data showthat the co-action of the secondary or co-antiknock additives is presentonly at small concentrations. In addition, it may also be seen that thegreatest benefit is obtained at very low metal ratios. (Metal ratio asused in the context of this specification refers to the weight ratio ofmetal in the secondary or co-antiknock agent to the lead in thetetraalkyllead when both are added to gasoline compositions inaccordance with the invention.)

The data in Table II also show that the secondary antiknock agents areeffective in concentrations ranging from as little as 0.5 milimole pergallon to as high as 10 milimoles per gallon. Even higher concentrationscan, of course, be used. However, it is apparent from these data thatthe octane number enhancement is reduced thereby. Even the optimumconcentration varies considerably with the particular co-antiknockmaterial which is used. The greatest octane number benefits obtained bythe co-anti knock agent in gasoline containing 3 cc. TEL per gallon areat concentrations of from about 1.0 to about 5.0 milli- 6 to about 0.065is particularly preferred. Though the foregoing examples have employedonly up to 6.0 cc. TEL/ gallon, the fuel compositions in accordance withthe invention may contain even greater amounts of tetraethylmoles ofmetal contained in the co-antiknock agent per lead, e.g., 12 cc. TEL/gallon and higher. gallon of fuel. Though the co-antiknock agents usedin accordance Though most COl'IlIl'lfiI'ClHl gasoline type fuels contamwith the invention are very eifective in isoparafiinic fuels, lead,usually at tetraethyllead, the amount varies Widely. their use is notlimited thereto. However, the composi- Generally, in the case ofautomotive fuels, the composition tion of the hydrocarbon fuel as toboiling range and eswill contain at least about 0.5 cc. TEL/ gallon andnot pecially hydrocarbon type exert a profound effect on the more thanabout 4.0 cc. TEL/ gallon, which is the maxiactivity of co-antiknockcompounds, which may be obmum permissible concentration in the UnitedStates beserved in the following example. cause of the extreme toxicityof TEL. In the case of EXAMPLE IV avaiation fuels, however, even higherTEL concentrations A laroe number of efi e h d 0 arb d t are used, e.g.,as high as 6.0 cc. TEL/gallon of fuel. c I n W Y r c on pro uc 5 iblended to different concentrations with motor gasohne Therefore, inorder to determine the efiect of lead conalk late which consisted of1007 b volum iso araffins centration on the co-antiknock activity of theforegoing y 1 e P 1 from the ainylation of butenes with isobutane.Duplicate discussed co-antlknock agents, the fo.low1ng test was per- 1 fh bl d b formed samp es 0 eac en were 0 tamed and t-etraethyllead wasadded to a concentration of 3 cc. TEL/gallon of EXAMPLE In blend.Additionally, copper diamyldithiocarbamate was A number of duplicatesamples of commercial buteneadded to one of each duplicate samples untilthe concenisobutane alkylate were prepared which contained amountstration of co-antiknock agent was 1.6 millimoles per galoftetraethyllead varying from 3 to 6 cc. TEL/gallon. lon of blend. TheResearch octane numbers of each set One of each duplicate sample wasthen divided into at of samples were then obtained and the differencebetween least four smaller samples to each of Which was added the octanenumbers of the samples with and without the from 0.5 to 5 millimoles/gallon of copper diamyldithiosecondary antiknock additive (A R.O.N.)were noted. carbamate. The Research octane numbers of all the sam- Theresults are given in the following tabulation.

TABLE III Hydrocarbon blending component Ooantiknoek agent Alltylate,

amount Increase in Amount in total Concenresearch Principal Boiling intotal blend tration O.N. on hydrocarbon Composition range blend (percent(mrnoles/ adding cotype F.) (percent vol.) gal.) antiknook vol.) agent(A R.O.N.)

100 1.6 3.0 saturates. 70% isopentane, of-

19.5 80.5 1.6 2.3 2.5 97.5 1.6 1.6 10.0 90.0 1.6 1.1 Mixed isoand 15.085. 0 1. 6 1. 8 Olefins Diisobutylene 5 95 1.6 4.3 Do 10 90 1.6 4.9130.- 15 85 1.6 3.7 130.. 20 80 1.6 2.2 Aromatics T0luene- 10 90 1.6 4.5Do 20 80 1.6 2.0 Therm 31 69 1.6 1.0 Alkyl benzenes 10 90 1.6 1.2 Alkylnaphthalenes. 10 90 1. 6 1. 2 Catalytic ref0rmate 10 90 1. 6 0. 3Tetrahydronaphthalene 380 1 99 1. 6 2. 6 D0 380 2 as 1.6 0.0Diarnylnaphth alone 400 1 99 1. 6 0. 0

ples were then determined. By subtracting the octane numbers of thesamples containing only TEL from the octane number of the samplescontaining co-antiknock agent and TEL (at the same concentration), ameasure of octane number enhancement (A R.O.N.) due to the presence ofthe co-antiknock agent was obtained which was then correlated as afunction of both co-antiknock concentration and TEL concentration.

The results, which are shown graphically in the drawing, show that theoptimum concentration of co-antiknock metal, in millirnoles per gallon,is about 1.5, 2.0 and 3 for the fuels containing 3, 4 and 6 cc. TEL/gallon, respectively. Since the optimum co-antilrnock concentration isessentially directly proportional to the primary anti-knockconcentration, it is apparent that the metal ratio of the two additives(as defined hereinbefore) is critical and is definitive of the operablerange of co-antiknock concentrations. Though metal ratios of as high as0.2 and even higher at large lead concentrations could be used, thepreferred range of metal ratio is from about 0.01 to about 0.10. A metalratio of from about 0.02

Efiect of Isa and Normal Paraffins on co-Amiknock Activity The additionof light isoparaffins, i.e., those having less than 8 carbon atoms permolecule, is beneficial to the action of the co-antiknock agent.However, the addition of heavier isoparatfins reduces the co-antiknockeffect considerably. It is therefore preferred that the gasolinecompositions in accordance with the invention not contain greater thanabout 20% by volume of isoparafiins boiling over about 300 F. It is evenfurther preferred that the gasoline composition contain no more thanabout 10% by volume of isoparaifins boiling above about 300 F.

Because of the detrimental effect of normal paraffins in reducing theoctane number, the gasoline compositions in accordance with theinvention preferably contain essentially no normal parafifins having 7or more atoms per molecule and only small amounts, preferably not over10%, of normal paraifins having 5 or 6 carbon atoms per molecule. Fuelcompositions containing essentially independent.

no normal paraffins having or more carbon atoms per molecule areparticularly preferred. Normal paraffins having less than 5 carbon atomsper molecule, for example, normal butane, having high octane numbers,are useful to provide the gasoline with proper vapor pressure and arenot deleterious to the action of the co-antiknock agents.

Effect of Cycloparaffins (Naphthenes) The gasoline compositions of theinvention should contain no more than by volume naphthenes boiling aboveabout 300 F., and preferably substantially none, because they aredelterious both with regard to blending octane number and their effecton the response of the co-antiknock agent. There is no limit, however,in the broad aspects of the invention, to the maximum concentration ofnaphthenes boiling below about 300 F.

Efiect of Olefins on Co-Antiknock Activity The incorporation of up toabout 10% of lighter olefins, especially those which are branched, isactually beneficial to the co-action of the co-antiknock agents withtetraethyllead. Moreover, the gasoline compositions of the invention canadvantageously contain up to 30% by volume olefins, but largerquantities are deleterious and should be avoided.

Effect of Aromatics Aromatics boiling below about 300 F., i.e., Caromatic hydrocarbons and lighter, have been found to be not greatlydelterious in minor concentrations, e.g., below about 50% by volume.Heavier aromatics, however, which boil above 300 F. are delterious andshould not exceed about by volume of the total gasoline blend. In fact,in order to obtain more practical benefits from the co-antiknock agent,it is preferred that the gasoline of the invention contain no more thanabout 10% by volume of aromatics boiling above 300 F., and no more than30% by volume of total aromatics.

Though the delterious efiect of high boiling aromatics on theeffectiveness of the co-antiknock additives is quite unfortunate, it hasbeen found that a very surprising relationship exits between the effectof heavy aromatics and the presence of light naphthenes. That is, lightnaphthenes suppress the deleterious effects of heavy aromatics. Inaccordance with applicants copending patent application Serial No.18,255, it is possible to have substantial amounts of aromatics boilingabove 300 F. in a base gasoline and still obtain large benefits fromcoantiknock additives, as long as light naphthenes, i.e., naphthenesboiling below about 300 F., are also incorporated in the base gasoline.

In general, it appears that one volume percent of light naphthenes canovercome completely the deleterious effect of one volume percent ofheavy aromatics. However, since practical benefits are obtained up to10% and 20% by volume heavy aromatics even in the absence of naphthenes,it is not necessary always to have present as much light naphthenes aswould be needed to completely cancel the effect of the heavy aromatics.The light naphthenes can be used to obtain even greater benefits fromthe co-antiknock additives in gasolines which must contain aromaticsboiling above 300 F. to have proper volatility distribution of highoctane number components. To take advantage of light naphthenes inaccordance with this preferred aspect of the invention, it is desirablethat the base gasoline contain at least 4% by volume, or preferably atleast /2% by volume, of naphthenes boiling below 300 F. for each 1% byvolume of aromatics boiling above 300 F. in excess of 10% by volume ofsuch aromatics, and preferably such amounts of light naphthenes for each1% by volume of all of such aromatics.

The adverse eifect of each of the deleterious or antagonisticcomponents, that is, aromatics, olefins, C plus normal parafiins andheavy naphthenes, is not however, Even with the use of naphthenes inaccord- A =A +1.3A +0.7A +0.25A 50+0.75N wherein A =percent by volume ofaromatics boiling below 300 A =percent by volume of aromatics boilingabove 300 A =percent by volume of olefins.

A =percent by volume of C plus normal paraflins and naphthenes boilingabove 300 F.

N =percent by volume of naphthenes boiling below 300 Summing up itsbroad aspects, the invention therefore resides in the discovery thatcompounds having the formula (zA- Y)...M as defined hereinbefore, areeffective as co-antiknock agents with tetraethyllead when both are addedto gasoline blends containing essentially no normal parafiins containing7 or more carbon atoms, no more than 10% by volume of C to C normalparaflins, no more than 20% by volume of isoparafiins boiling above 300F., no more than 10% by volume of naphthenes boiling above 300 F., nomore than 30% by volume olefins, no more than 50% by volume of totalaromatics and no more than 20% by volume of aromatics boiling above 300F., the composition of the gasoline blends being within the limitsdefined by the empirical relationship Component: Percent by weightTetraethyllead 61.48 Ethylene dibromide (0.5 theory) 17.86 Ethylenedichloride (1.0 theory) 18.81 Dye 0.06 Kerosene and impurities 1.79

The co-antiknock materials of the invention are, however, equallyeffective in leaded gasoline containing pure TEL with no halohydrocarbonscavenger, or in leaded gasoline containing TEL with ethylene dibromide(e.g., 1.0 theory) and no ethylene dichloride.

Besides the aforementioned halogen-containing lead scavengers, the fuelcompositions of the invention can, and ordinarily will, contain otheradditives, for example, dyes, spark plug antifoulants such as tricresylphosphate, dimethyl xylyl phosphate, and diphenyl cresyl phosphate,combustion modifiers such as alkyl boronic acids and lower alkylphosphates and phosphites, oxidation inhibitors such asN,N-disalicylal-1,Z-propanediamine, and rust inhibitors such aspolymerized linoleic acids and N,C- disubstituted imidazolines, and thelike.

It is to be understood that the order of mixing the various constituentsof the compositions of the invention is immaterial. For example, theco-antiknock compound may be added to a gasoline which already containsthe tetraethyllead primary antiknock material. Likewise, theco-antiknock and primary antiknock compounds may be first mixed, stored,and handled as a concentrate, and added to the gasoline at a later time.A gasoline additive concentrate of this latter type may also containhalogen scavenger and spark plug antifouling compound. Under othercircumstances, it may be desirable to mix the halogen scavenger and theprimary antiknock compound, or the primary antiknock and co-antiknockcompounds, in the desired relative proportions and handle or store thismixture, with or without stabilizers, antifouling compounds, inhibitors,etc., as a concentrate for incorporation with the other components ofthe ultimate fuel composition.

When an additive concentrate of this latter type is employed, it ispreferred that it contain an optimum or near optimum metal ratio. Such aconcentrate will therefore contain from 0.01 to 0.10 gram of metal inthe co-antiknock agent per gram of lead in the tetraethyllead.Preferably, such a concentrate contains from about 0.02 to about 0.065gram of metal per gram of lead.

A typical additive concentrate in accordance with the invention andcontaining both TEL motor mix and phosphorus compound for ignitioncontrol as well as co-antiknock agent has the following composition:

Component: Percent by weight Tetraethyllead 49.0-58.9 Ethylene dibromide14.2-17.1 Ethylene dichloride 15.0-18.1 Phosphorus (as tricresylphosphate) 3.8-12.5 Copper (as copper diamyldithioc-arba mate) 0.4-7.9Kerosene, dye, impurities 1.4-1.7

We claim as our invention:

1. A motor gasoline fuel composition consisting essentially of a mixtureof hydrocarbons having an ASTM boiling range below about 400 R, anoctane numberimproving amount of tetraethyllead, and a co-antiknockagent having the structural formula wherein M is a metal selected fromthe group consisting of antimony, bismuth, cobalt, copper, nickel, andtellurium, Y is a chalcogen atom having an atomic number of from 8 to16, inclusively, A is selected from the group consisting of carbon andphosphorus, Z is selected from the group consisting of (RY) when A isphosphorus and (R X) when A is carbon, X is selected from the groupconsisting of nitrogen and chalcogen having an atomic number of from 8to 16, inclusively, R is a monovalent hydrocarbyl radical containingfrom 3 to 15 carbon atoms per molecule, n is a whole number of from 1 to2 which is one less than the valence of X, and m is -a whole numbercorresponding to the valence of the metal M, the amount of co-antiknockagent corresponding to from about 0.01 to about 0.10 gram of metalcontained in the co-antiknock agent per gram of lead contained in thetetraethyllead, said mixture of hydrocarbons being comprised of (1) nomore than 50% by volume aromatics, (2) no more than about 30% by volumeolefins, (3) no more than about 20% by volume each of isoparatfins andaromatics boiling above about 300 F., (4) no more than about 10% byvolume each of normal paraffins having 5 to 6 carbon atoms per moleculeand naphthenes boiling above about 300 F., and (5) essentially no normalparaffins having greater than 6 carbon atoms per molecule, and furthercharacterized as having an equivalent amount of co-antiknock antagonists(A not exceeding 50+ 0.75N wherein A and N are defined as hereinbeforein the specification.

2. The fuel composition of claim 1 which is comprised of (1) no morethan about 30% by volume of aromatics, (2) no more than about 20% byvolume each of olefins and aromatics boiling above about 300 F., (3) nomore than about 10% by volume each of isoparafiins boiling above about300 and naphthenes boiling above about 300 F., and (4) essentially nonormal parafiins having greater than 4 carbon atoms per molecule, andfurther characterized as having an equivalent amount of co-antiknockantagonists (A not exceeding 50+0.75N wherein A and N are defined ashereinbefore in the specification.

3. The motor gasoline fuel composition of claim 1 in which M is a metalhaving an atomic number of from 27 to 29, inclusively.

4. The motor gasoline fuel composition of claim 1 in which M is copper.

5. The motor gasoline fuel composition of claim 1 in which theco-antiknock agent is a metal dialkyldithiocarbamate in which the alkylgroups each contain from 4 to 8 carbon atoms.

6. The motor gasoline fuel composition of claim 5 in which theco-antiknock agent is copper dialkyldithiocarbamate.

7. The motor gasoline fuel composition of claim 5 in which theco-antiknock agent is nickel dialkyldithiocarbamate.

8. The motor gasoline fuel composition of claim 5 in which theco-antiknock agent is cobalt diallkyldithiocarbamate.

9. The motor gasoline fuel composition of claim 5 in which theco-antiknock agent is antimony dialkyldithiocarbamate.

10. The motor gasoline fuel composition of claim 5 in which theco-antiknock agent is copper dialkyldithiocarbamate.

11. The motor gasoline fuel composition of claim 5 in which theco-antiknock agent is tellurium dialkyldithiocarbamate.

12. The motor gasoline fuel composition of claim 5 in which theco-antiknock agent is bismuth dialkyldithiocarbamate.

13. The motor gasoline fuel composition of claim 1 in which theco-antiknock agent is a metal 0,0-dialkylthionothiophosphate.

14. The motor gasoline fuel composition of claim 13 in which theco-antiknock agent is copper 0,0-dilaurylthionothiophosphate.

15. A gasoline additive concentration composition consisting essentiallyof a mixture of tetraethyllead and a coantiknock agent having thestructural formula wherein M is a metal selected from the groupconsisting of antimony, bismuth, cobalt, copper, nickel, and tellurium,Y is a chalcogen atom having an atomic number of from 8 to 16,inclusively, A is selected from the group consisting of carbon andphosphorus, Z is selected from the group consisting of (RY) when A isphosphorus and (R X) when A is carbon, X is selected from the groupconsisting of nitrogen and chalcogen having an atomic number of from 8to 16, inclusively, R is a monovalent hydrocarbyl radical containingfrom 3 to 15 carbon atoms per molecule, n is a whole number of from 1 to2 which is one less than the valence of X, and m is a whole numbercorresponding to the valence of the metal M, the amount of co-antiknockagent corresponding to from about 0.01 to about 0.10 gram of metalcontained in the co-antiknock agent per gram of lead contained in thetetraethyllead.

(References on following page) 1 1 1 2 References Cited in the file ofthis patent FOREIGN PATENTS UNITED STATES PATENTS 746,036 Great BritainMar. 7, 1956 2,023,372 Max Dec. 3, 1935 2,086,775 Lyons et a1. July 13,1937 5 OTHER REFERENCES igg i a Improved Motor Fuels through SelectiveBlending, 2314575 D Oran i 1943 by Wagner et a1. Paper presented before22nd Annual 2 398 282 Bartholoir i ev v Apr. 9 1946 Meeting of theAmerican Petroleum Institute, Nov. 7, 2,546,421 Bartholomew Mar. 27,1951 10 3 P 2,552,570 McNab et aL May 15, 1951 Avlatlon GasolineManufacture, by Van Winkle, first 2 1 417 Brown et 1 31 1957 ed, 1944,MeGraw-Hill B ok Co., pp. 43-63 and 197- 2,901,336 Brown Aug. 25, 19592,913,413 Brown Nov. 17, 1959

1. A MOTOR GASOLINE FUEL COMPOSITION CONSISTING ESSENTIALLY OF A MIXTUREOF HYDROCARBONS HAVING AN ASTM BOILING RANGE BELOW ABOUT 400*F., ANOCTANE NUMBERIMPROVING AMOUNT OF TETRAETHYLLEAD, AND A CO-ANTIKNOCKAGENT HAVING THE STRUCTURAL FORMULA